The risk of acute disseminated encephalomyelitis (ADEM) following covid-19 vaccination in England: A self-controlled case-series analysis

Figures & data

Table 1. Description of the 215 individuals with an ADEM diagnosis from SUS in the period 8th December 2020 to 31st March 2023.

Factor	Level	Frequency of Identified ADEMs (n = 215)	% of Identified ADEMs
Period (year-quarter)	2020–4 (from Dec 8th)	6	2.8%
	2021–1	30	14.0%
	2021–2	27	12.6%
	2021–3	20	9.3%
	2021–4	24	11.2%
	2022–1	23	10.7%
	2022–2	21	9.8%
	2022–3	23	10.7%
	2022–4	26	12.1%
	2023–1	15	7.0%
Age-years	5 to 9	39	18.1%
	10 to 19	45	20.9%
	20 to 39	47	21.9%
	40 to 64	63	29.3%
	65+	21	9.8%
Sex	Male	100	46.5%
	Female	115	53.5%
Clinically Vulnerable or Immunosuppressed	No	176	81.9%
	Yes	41	19.1%
Ethnicity	White	157	73.0%
	Asian or Asian British	29	13.5%
	Black African, Caribbean or Black British	8	3.7%
	Mixed or Multiple Ethnic Groups	6	2.8%
	Not Known or Other	15	7.0%
Ever Vaccinated	No	66	30.7%
	Yes (and first dose ChAdOx1-S)	73	34.0%
	Yes (and first dose mRNA)	76	35.3%

Table 2. Relative incidence of ADEM by vaccine type and dose.

Vaccine Type	Description	Risk Window	Person Days	Events	Relative Incidence (95% Confidence Interval)
Control time	Baseline	none	160,145	184	Base
Pre-vaccine 14 day windows*	Removed	−14 to −1	3717	1	n/a
ChAdOx1-S	Vaccine dose 1	0–42 days	3136	12	3.13 (1.56–6.25)
	Vaccine dose 2	0–42 days	2494	1	0.36 (0.05–2.68)
mRNA	Vaccine dose 1	0–42 days	3196	3	0.78 (0.24–2.50)
	Vaccine dose 2	0–42 days	2838	6	1.77 (0.76–4.13)
	Vaccine dose 3 or 4	0–42 days	4515	7	1.26 (0.56–2.85)
	Bivalent vaccine BA1/2	0–42 days	1419	3	1.98 (0.58–6.80)

*Pre-vaccination period 1–14 days prior to vaccine was removed to account for individuals not getting vaccinated due to being in hospital for ADEM.

Data availability statement

The raw study data are protected and are not available due to data privacy laws. This work is carried out under Regulation 3 of The Health Service (Control of Patient Information) (Secretary of State for Health, 2002)³ using patient identification information without individual patient consent. Data cannot be made publicly available for ethical and legal reasons, i.e. public availability would compromise patient confidentiality as data tables list single counts of individuals rather than aggregated data.